a. Field of the Invention
This invention pertains generally to imaging systems and methods and more particularly to a system and method for reproduction of an image scanned by a beam.
b. Description of the Prior Art
When an image on a medium is scanned for conversion to an electrical video signal, the modulation transfer function of the video signal is limited in bandwidth by the target area or size of the beam, scattering of light in the medium, and the bandwidth of the circuitry in which the video signal is generated and processed. This limited bandwidth can result in inadequate resolution for proper reproduction of the image. This problem arises, for example, at the boundaries between areas of different color density in halftone images scanned in a laser engraving system. The level of the video signal at the boundaries varies with the width and color levels of the areas, and consequently the boundaries cannot be detected by a simple level detector.
Heretofore, the boundaries between areas of different color density have been detected by changes in the slope of the video signals. However, this technique has not provided satisfactory results because the magnitude of the change in slope is dependent upon the width of the colored areas and the magnitude of the video signal, as well as the change in color itself. Accordingly, it has not been possible to determine the positions of the boundaries accurately with a slope detector.